100 строки
4.2 KiB
Groff
100 строки
4.2 KiB
Groff
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.\"Copyright 2006, Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.TH MPI_Sendrecv_replace 3OpenMPI "September 2006" "Open MPI 1.2" " "
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.SH NAME
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\fBMPI_Sendrecv_replace\fP \- Sends and receives a message using a single buffer.
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.SH SYNTAX
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.ft R
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.SH C Syntax
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.nf
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#include <mpi.h>
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int MPI_Sendrecv_replace(void *\fIbuf\fP, int\fI count\fP, MPI_Datatype\fI datatype\fP,
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int\fI dest\fP, int\fI sendtag\fP, int\fI source\fP, int\fI recvtag\fP, MPI_Comm\fI comm\fP,
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MPI_Status\fI *status\fP)
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.SH Fortran Syntax
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.nf
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INCLUDE 'mpif.h'
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MPI_SENDRECV_REPLACE(\fIBUF, COUNT, DATATYPE, DEST, SENDTAG, SOURCE,
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RECVTAG, COMM, STATUS, IERROR\fP)
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<type> \fIBUF\fP(*)
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INTEGER \fICOUNT, DATATYPE, DEST, SENDTAG\fP
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INTEGER \fISOURCE, RECVTAG, COMM\fP
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INTEGER \fISTATUS(MPI_STATUS_SIZE), IERROR\fP
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.SH C++ Syntax
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.nf
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#include <mpi.h>
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void Comm::Sendrecv_replace(void* \fIbuf\fP, int \fIcount\fP, const
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Datatype& \fIdatatype\fP, int \fIdest\fP, int \fIsendtag\fP, int \fIsource\fP,
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int \fIrecvtag\fP, Status& \fIstatus\fP) const
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void Comm::Sendrecv_replace(void* \fIbuf\fP, int \fIcount\fP, const
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Datatype& \fIdatatype\fP, int \fIdest\fP, int \fIsendtag\fP, int \fIsource\fP,
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int \fIrecvtag\fP) const
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.SH INPUT/OUTPUT PARAMETER
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.ft R
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.TP 1i
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buf
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Initial address of send and receive buffer (choice).
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.SH INPUT PARAMETERS
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.ft R
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.TP 1i
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count
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Number of elements in send and receive buffer (integer).
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.TP 1i
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datatype
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Type of elements to send and receive (handle).
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.TP 1i
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dest
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Rank of destination (integer).
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.TP 1i
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sendtag
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Send message tag (integer).
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.TP 1i
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source
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Rank of source (integer).
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.TP 1i
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recvtag
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Receive message tag (integer).
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.TP 1i
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comm
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Communicator (handle).
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.SH OUTPUT PARAMETERS
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.ft R
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.TP 1i
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status
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Status object (status).
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.TP 1i
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IERROR
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Fortran only: Error status (integer).
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.SH DESCRIPTION
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.ft R
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The send-receive operations combine in one call the sending of a message to one destination and the receiving of another message, from another process. The two (source and destination) are possibly the same. A send-receive operation is useful for executing a shift operation across a chain of processes. If blocking sends and receives are used for such a shift, then one needs to order the sends and receives correctly (for example, even processes send, then receive; odd processes receive first, then send) in order to prevent cyclic dependencies that may lead to deadlock. When a send-receive operation is used, the communication subsystem takes care of these issues. The send-receive operation can be used in conjunction with the functions described in Chapter 6 of the MPI Standard, "Process Topologies," in order to perform shifts on various logical topologies. Also, a send-receive operation is useful for implementing remote procedure calls.
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.sp
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A message sent by a send-receive operation can be received by a regular receive operation or probed by a probe operation; a send-receive operation can receive a message sent by a regular send operation.
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.sp
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MPI_Sendrecv_replace executes a blocking send and receive. The same buffer is used both for the send and for the receive, so that the message sent is replaced by the message received.
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.sp
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The semantics of a send-receive operation is what would be obtained if the caller forked two concurrent threads, one to execute the send, and one to execute the receive, followed by a join of these two threads.
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.SH ERRORS
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Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI:Exception object.
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.sp
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Before the error value is returned, the current MPI error handler is
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called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.
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.SH SEE ALSO
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.ft R
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.sp
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MPI_Sendrecv
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' @(#)MPI_Sendrecv_replace.3 1.20 06/03/09
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